1. Field of the Invention
The present invention relates generally to crossbows, and more specifically, to a mechanism for releasing the bowstring of a crossbow to fire an arrow.
2. Description of the Related Art
Crossbows have also long been known in the archery field for use in hunting game. Crossbows have higher draw weights than conventional archery bows and fire arrows (or “bolts”) with greater speeds. As a result, crossbows usually have greater range than an archery bow.
When crossbows are configured for firing, the force exerted by the retracted bowstring can be in the range of approximately 100 to 200 pounds. The trigger assembly of the crossbow must be capable of holding the bowstring in firing position, while allowing the bowstring to be released as the user pulls the trigger. This often results in an excessive pull force which the user must exert upon the trigger of the crossbow to fire the arrow, which in turn decreases the accuracy of the shot.
Crossbows can be relatively heavy, making them more difficult to carry and operate quickly. Complex trigger mechanisms and bowstring retraction systems often contribute to such excessive weight.
U.S. Pat. No. 6,095,128, to Bednar, shows and describes a crossbow that includes an integrated bowstring draw mechanism. The bowstring is drawn back along the barrel, or stock, of the crossbow by a drawing mechanism integrated into the tailstock of the crossbow. The drawing mechanism is operated by a hand crank inserted into the tailstock of the crossbow. A claw is engaged over the bowstring, and the claw is retracted rearward by a pair of cables to pull the bowstring into a trigger mechanism that selectively holds and releases the bowstring. The cables attached to the claw extend back to the drawing mechanism housed in the tailstock of the crossbow. Once the bowstring is pulled back into engagement with the trigger mechanism, the drawing mechanism is released, and the claw is removed from the bowstring. An arrow is inserted into the crossbow, nocked with the bowstring, and rests upon the upper surface of the barrel in preparation for firing. The upper surface of the barrel includes a central channel or arrow guide, and the arrow slides along the arrow guide when the arrow is fired. This is often referred to as the “rail” of the barrel. This need to remove the claw from the bowstring after engaging the bowstring with the trigger mechanism requires additional time between shots of the crossbow.
U.S. Pat. No. 5,598,829, to Bednar, shows and describes a trigger mechanism designed for use in a crossbow. The bowstring is drawn back by a drawing mechanism and engaged with a string release latch. The string release latch is normally biased toward a release position by a spring. The string release latch is releasably coupled, via sear surfaces and a rocker latch, to the crossbow trigger. Rearward force of the bowstring against the string release latch causes the string release latch to pivot toward its cocked position and resets the trigger. The drawing mechanism is then removed from the bowstring, and the bowstring is retained by the string release latch until the trigger is pulled.
As demonstrated by the above-referenced patents to Bednar, the customary practice in the field of crossbows is to secure a bowstring release latch at a fixed point near the rear of the crossbow, adjacent the trigger of the crossbow, and to draw the bowstring back into engagement with the fixed-position bowstring release latch. The drawing mechanism must then be removed from the bowstring, and perhaps stored, before the crossbow can be fired. Moreover, the bowstring release latch must be in physical contact, via one or more sear surfaces, with the trigger to retain the bowstring in firing position. Again, this requirement often results in the need for the user to exert excessive finger pull pressure on the trigger to release the bowstring, particularly when the crossbow has a relatively high draw weight.
Other methods for drawing and firing the bowstring of a crossbow have also been proposed. For example, in U.S. Pat. No. 4,603,676, to Luoma, a crossbow is described wherein the trigger is incorporated within a movable housing that resembles the handle of a caulking gun. The movable housing includes a cocking handle that can be reciprocated to move the housing (including the trigger) rearward along a drawback rod that extends rearward from the riser of the crossbow. The housing is initially moved forward along the drawback rod to engage the bowstring with the trigger mechanism. The cocking handle is then squeezed and released a number of times to move the housing, trigger, and bowstring, rearward along the drawback rod in stepwise increments until reaching the fully drawn position, at which time, an arrow may be loaded and fired. The cocking mechanism disclosed by Luoma does not permit rapid retraction of the bowstring, and the drawback rod does not appear to be sufficiently sound to bear significant draw weights while ensuring an accurate shot.
Stryker Manufacturing of Eugene, Oregon has offered a crossbow under the brand name “Stryker” wherein a bowstring hook is secured to a chain for sliding motion along the barrel and rail of the crossbow. The chain is disposed below the rail, and a winding crank is used to move the chain forward and rearward. To draw the bowstring back, the crank is operated to move the chain and attached string carrier forward until the string carrier reaches the bowstring. The Stryker owner's manual states that the user should crank the crossbow approximately 40 revolutions, while depressing a thumb pawl, before the string carrier reaches its forward-most position adjacent the bowstring. The user then manually closes the string hook over the bowstring. The thumb pawl is then released, and the crank is rotated in the opposite direction to draw the string carrier and bowstring rearward until reaching a fully-drawn position. An arrow is then loaded onto the rail and slid under a hold down spring to be nocked with the bowstring. In the fully-cocked position, the string carrier is disposed proximate to the crossbow trigger, and the operation of the trigger causes the string carrier to release the bowstring and fire the arrow. After firing, the above-described procedure must be repeated to fire another arrow. The chain drive retraction system used by the Stryker-brand bow results in extended times for firing a second arrow after a first arrow is fired, primarily because the crank must be operated in order to move the string carrier forward to engage the bowstring. In addition, the requirement for loading the arrow upon a rail, and the resulting frictional forces between the arrow and the rail during firing, limit the arrow speed that can be produced by such a crossbow.
Accordingly, it is an object of the present invention to provide a crossbow which releases the bowstring in an accurate, consistent, and repeatable manner.
Another object of the present invention is to provide such a crossbow which avoids the need for a user to exert excessive trigger pull force to release the bowstring, and wherein the trigger pull force can be made independent of the draw weight of the bowstring.
Still another object of the present invention is to provide such a crossbow having a bowstring release and bowstring draw mechanism that are relatively light in weight, compact, easy to operate, relatively inexpensive, and compatible with anti-dry fire safeguards.
A further object of the present invention is to provide such a crossbow which avoids the need to remove and store a bowstring draw mechanism before firing an arrow.
A yet further object of the present invention is to provide such a crossbow that avoids the necessity for the arrow to slide along a top rail, and thereby avoids frictional forces that otherwise result between the arrow and the top rail.
Yet another object of the present invention is to provide such a crossbow that allows a user to quickly engage the bowstring with a draw mechanism in preparation for pull-back to the drawn position, and to quickly retract the bowstring to the fully-drawn position, thereby reducing the time between firing a first arrow and firing a second arrow.
These and other objects of the present invention will become more apparent to those skilled in the art as the description thereof proceeds.